/*
 * This file is part of "JTA - Telnet/SSH for the JAVA(tm) platform".
 *
 * (c) Matthias L. Jugel, Marcus Meißner 1996-2005. All Rights Reserved.
 *
 * Please visit http://javatelnet.org/ for updates and contact.
 *
 * --LICENSE NOTICE--
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * --LICENSE NOTICE--
 *
 */
package de.mud.ssh;

import java.io.IOException;
import java.security.SecureRandom;

/**
 * @author Marcus Meissner
 * @version $Id: SshMisc.java 499 2005-09-29 08:24:54Z leo $
 */
public class SshMisc
{
    /**
     * return the strint at the position offset in the data First 4 bytes are
     * the length of the string, msb first (not including the length itself).
     * The following "length" bytes are the string value. There are no
     * terminating null characters.
     */
    static public String getString(int offset, byte[] byteArray)
	    throws IOException
    {

	short d0 = byteArray[offset++];
	short d1 = byteArray[offset++];
	short d2 = byteArray[offset++];
	short d3 = byteArray[offset++];

	if (d0 < 0)
	    d0 = (short) (256 + d0);
	if (d1 < 0)
	    d1 = (short) (256 + d1);
	if (d2 < 0)
	    d2 = (short) (256 + d2);
	if (d3 < 0)
	    d3 = (short) (256 + d3);

	int length = d0 * 16777216 // to be checked
		+ d1 * 65536 + d2 * 256 + d3;
	String str = ""; // new String(byteArray,0);
	for (int i = 0; i < length; i++)
	{
	    if (byteArray[offset] >= 0)
		str += (char) (byteArray[offset++]);
	    else
		str += (char) (256 + byteArray[offset++]);
	}
	return str;
    }

    static public byte getNotZeroRandomByte()
    {
	byte[] randomBytes = new byte[32];

	SecureRandom random = new java.security.SecureRandom(randomBytes);
	while (true)
	{
	    random.nextBytes(randomBytes);
	    for (int i = 0; i < randomBytes.length; i++)
		if (randomBytes[i] != 0)
		    return randomBytes[i];
	}
    }

    static public byte[] addArrayOfBytes(byte[] a, byte[] b)
    {
	if (a == null)
	    return b;
	if (b == null)
	    return a;
	byte[] temp = new byte[a.length + b.length];
	for (int i = 0; i < a.length; i++)
	    temp[i] = a[i];
	for (int i = 0; i < b.length; i++)
	    temp[i + a.length] = b[i];
	return temp;
    }

    static public byte[] XORArrayOfBytes(byte[] a, byte[] b)
    {
	if (a == null)
	    return null;
	if (b == null)
	    return null;
	if (a.length != b.length)
	    return null;
	byte[] result = new byte[a.length];
	for (int i = 0; i < result.length; i++)
	    result[i] = (byte) (((a[i] & 0xff) ^ (b[i] & 0xff)) & 0xff);// ^ xor
									// operator
	return result;
    }

    /**
     * Return the mp-int at the position offset in the data First 2 bytes are
     * the number of bits in the integer, msb first (for example, the value
     * 0x00012345 would have 17 bits). The value zero has zero bits. It is
     * permissible that the number of bits be larger than the real number of
     * bits. The number of bits is followed by (bits + 7) / 8 bytes of binary
     * data, msb first, giving the value of the integer.
     */

    static public byte[] getMpInt(int offset, byte[] byteArray)
	    throws IOException
    {

	byte[] MpInt;

	short d0 = byteArray[offset++];
	short d1 = byteArray[offset++];

	if (d0 < 0)
	    d0 = (short) (256 + d0);
	if (d1 < 0)
	    d1 = (short) (256 + d1);

	int byteLength = (d0 * 256 + d1 + 7) / 8;
	MpInt = new byte[byteLength];
	for (int i = 0; i < byteLength; i++)
	    MpInt[i] = byteArray[offset++];
	return MpInt;
    } // getMpInt

    /**
     * Return a Arbitrary length binary string First 4 bytes are the length of
     * the string, msb first (not including the length itself). The following
     * "length" bytes are the string value. There are no terminating null
     * characters.
     */
    static public byte[] createString(String str) throws IOException
    {

	int length = str.length();
	byte[] value = new byte[4 + length];

	value[3] = (byte) ((length) & 0xff);
	value[2] = (byte) ((length >> 8) & 0xff);
	value[1] = (byte) ((length >> 16) & 0xff);
	value[0] = (byte) ((length >> 24) & 0xff);

	byte[] strByte = str.getBytes();

	for (int i = 0; i < length; i++)
	    value[i + 4] = strByte[i];
	return value;
    } // createString

    /**
     * This table simply represent the results of eight shift/xor operations for
     * all combinations of data and CRC register values. In other words, it
     * caches all the possible resulting values such that they won't need to be
     * computed.
     */
    static private long crc32_tab[] =
    { 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
	    0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
	    0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
	    0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
	    0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
	    0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
	    0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
	    0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
	    0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
	    0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
	    0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
	    0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
	    0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
	    0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
	    0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
	    0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
	    0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
	    0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
	    0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
	    0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
	    0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
	    0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
	    0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
	    0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
	    0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
	    0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
	    0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
	    0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
	    0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
	    0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
	    0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
	    0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
	    0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
	    0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
	    0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
	    0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
	    0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
	    0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
	    0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
	    0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
	    0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
	    0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
	    0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
	    0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
	    0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
	    0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
	    0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
	    0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
	    0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
	    0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
	    0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
	    0x2d02ef8dL };

    /**
     * Compute the crc Cyclic Redundancy Check, with the polynomial 0xedb88320,
     * The polynomial is
     * X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 We
     * take it "backwards" and put the highest-order term in the lowest-order
     * bit. The X^32 term is "implied"; the LSB is the X^31 term, etc. The X^0
     * term (usually shown as "+1") results in the MSB being 1. so the poly is
     * 0x04c11db7 (used for Ethernet) The buf will be the Padding, Packet type,
     * and Data fields. The crc is computed before any encryption. R =X^n * M
     * rem P M message P polynomial crc R : crc calculated. T(x) = x^n * M(x) +
     * R(x) property: T rem P = 0
     */

    // Return a 32-bit CRC of the byte using the feedback terms table
    static public long crc32(byte[] s, int len)
    {
	int i;
	long crc32val = 0;
	for (i = 0; i < len; i++)
	{
	    crc32val = crc32_tab[(int) ((crc32val ^ s[i]) & 0xff)]
		    ^ (crc32val >> 8);
	}
	return crc32val;
    }

}
